Temperature equalizing means for a plurality of conduits



F. FULLER, JR 3,117,620

TEMPERATURE EQUALIZING MEANS FOR A PLURALITY 0F coununs Jan. 14, 1964 3Sheets-Sheet 1 Filed Jan. 4, 1960 ATTORN Y Jan. 14,1964 FULLER, JR3,117,620 TEMPERATURE EQUALIZING MEANS FOR A PLURALITY OF CONDUITS FiledJan. 4, 1960 v 3 Sheets-Sheet 2 8 2 AMPLIFIER INVENTOR FOR/V5) F ULLE RJR.

ATTORNEY Jan. 14, 1964 F. FULLER, JR

TEMPERATURE EQUALIZING MEANS FOR A PLURALITY 0F CONDUITS Filed Jan.'4,1960 3 Sheets-Sheet 3 AMPLIFIER INVENTOR FORNEY FULLER, JR

ATTORNEY United States Patent 3,117,620 TEMPERATURE EQUALIZZING MEANSFOR A PLURALITY 0F CONDUlTS Forney Fuller, J12, 6959 Canal Blvd, NewOrleans, La. Fiied fan. 4, 1960, Ser. No. 112 3 Claims. (Cl. 165-40)This invention relates to steam heaters of the type known in the powerart as superheaters and reheaters. Superheaters and reheaters are heattransfer devices through which steam passes to absorb heat and thusraise the steam to a desired temperature. A superheater heats saturatedsteam after it leaves the evaporating section of a boiler for admissionto a turbine. A reheater heats steam which has been bled from onesection of a steam turbine for reintroduction to the turbine at anothersection thereof. The invention concerns an improvement to bothsuperheaters and reheaters and hence the following description willtreat these two devices as synonyms.

More specifically, the invention relates to a scheme for equalizing thetemperatures in each of a plurality of conduits which connect the inletand outlet headers in a stream heater. By equalizing these temperatures,each conduit will conduct the steam to be heated which passestherethrough at the maximum temperature which the metal from which theconduits are fashioned may withstand without failure. As well known toworkers in the power art, the higher the temperature of the steampassing through a prime mover, the greater the latters efiiciency.

In stearn heaters there are several factors which give rise to unequaltemperatures in the various conduits. The temperature of the heatervaries with burner design, air flow to the burners, fuel flow to theburners and furnace arrangement. Varying gas flow patterns across theheater exist due to furnace design and heat absorbing arrangement in thefurnace, heater and boiler. Nonuniform ash and slag accumulations on theheater conduits cause non-uniform heat absorbing surfaces thereon. Theinternal design of steam drums and steam headers causes different steamflow patterns through the conduits. Conduit design sometimes dictatesdifferent conduit configurations, thus causing difierent steam pathsthrough the heating gas. Non-uniform operation of soot blowers resultsin non-uniform heat transfer to the conduits.

According to the invention an orifice of variable area is placed in eachheater conduit. A temperature sensing element, which may be located nearthe orifice or at a point in the conduit remote therefrom, controls theflow through the orifice in accordance with the temperature sensed.Varying the steam flow through the conduit varies the temperaturethereof. By such an arrangement, the operating temperature of eachconduit in the steam heater may be made to be the maximum for the metalfrom which it is fashioned, thereby effecting optimum heat transfer.

In the drawings:

FIG. 1 is a partial cross-section of a conventional separately-firedsteam heater showing the provision of one conduit with a variableorifice and temperature sensing element.

FIG. 2 is a view taken along line 22 of FIG. 1 showing the plurality ofstream conduits Within the steam heater.

FIG. 3 is a cross section of a steam conduit showing an embodiment of avariable orifice and temperatures sensing element.

FIG. 4 is a view taken along section 4-4 of FIG. 3.

FIG. 5 is a view taken along section 55 of FIG. 3.

FIG. 6 is a cross-section of a steam conduit, similar to that of FIG. 3,showing a second embodiment of a variable orifice and temperaturesensing element.

FIG. 7 is a view along section 77 of FIG. 6.

FIG. 8 is a view along section 88 of FIG. 6.

Referring now to FIGS. 1 and 2 of the drawings, the numeral 16 denotes aseparately fired steam heater which houses a plurality of parallel steamconduits extending between and joining an inlet header 12 and an outletheader 14. The shown steam conduit (similar to the others) is denoted bythe numeral 16 and is provided at its interior with an orifice ofvariable opening shown at point 17 therealong (disclosed in more detailhereinafter) and temperature sensing means for its control at point 18therealong. Suitable circuitry is provided between the sensing elementand the orifice of variable opening.

In operation, steam at a given temperature from inlet header 12 passesthrough the conduit 16, is heated during this passage by hot gases inthe heater 10, and exits through outlet header 14. In the event that thesteam temperature at point 18 is greater than that permissible for themetal of the conduit, the flow passage opening of the orifice at point17 increases allowing a greater flow rate through the conduit. A greaterflow rate causes the conduit temperature to diminish since the inletsteam is at a lower temperature than that of the gases within the heater10.

In the event that the temperature of the steam at point 18 is less thanthe allowable maximum for the particular conduit metal employed, thetemperature sensing element causes the flow passage opening of theorifice at point 17 to diminish, causing a lesser fiow rate through theconduit. A lesser flow rate results in an increase of conduittemperature, since the inlet steam dwells within the conduit for alonger time, thereby absorbing more heat from the gases within theheater 10.

By suitable relation (to be given later in detail) of the orifice 17 andtemperature element sensing at 18, a given steady state or operatingtemperature for each conduit 16 may be realized in spite of the aboveenumerated factors which usually act to cause their variance.

The remaining description will dwell upon the two embodiments of FIGS. 3to 8.

Referring now to FIGS. 3 to 5 of the drawings, the numeral 6%) denotes asteam conduit provided internally with a curved stationary member 62having apertures 64, 66, and 68. A stem 76 extends through segment 60and carries a curved element 72 at its lower end. Element 72 is providedwith an aperture 74. A spiral Monel or other suitable metal tube 76 isconnected at its lower end to stem 79 and at its upper end to a housing78 provided with a coolant chamber 79. Guides 86 surround stem 70. Aresistance heating coil, not shown, is located within coil 76 and isconnected to an electrical amplifier 82. A thermocouple element 84, forsensing temperature, is located along the conduit 66 and is connected tothe amplifier.

During normal or steady state operation, steam passes through apertures64 and 66. In the event the conduit temperature increases beyond adesired level, thermocouple 84 senses the increase and, by suitablecircuitry in 82, the resistance coil within tube 76 is energized,causing the tube to expand and rotate. Such rotation is transmittedthrough stem 76 and aperture 74 moves into at least partial coincidencewith aperture 68. Also downward motion of coil 76 increases the flowthrough aperture 66 just above element 72. These two motions allow agreater rate of steam flow with consequent lessening of steamtemperature.

In the event of a decrease in desired conduit temperature, tube coil 76contracts due to the effect of coolant in chamber 79 and the flowthrough aperture 66 is diminished due to the upward travel of element72. Contraction of coil 76 is also accompanied by rotation of element72,

but in the opposite direction and hence apertures 68 and 74 do not comeinto coincidence. With a diminished flow rate through aperture 66 thesteam temperature rises.

Preferably, thermocouple 84 is placed near an outlet header while theother elements are placed near an inlet header, to subject them to lowersteam temperatures.

Referring now to the embodiment shownin FIGS. 6 to 10, the numeral 90denotes a steam conduit provided internally with a disc 92 having anintegral tongue portion 94. A The disc has an aperture 96 and anaperture 98 on its tongue portion. An arm 1% is pivoted on pin 182carried by disc 92 and carries a conical plug 184 which extendspartially into aperture 98. Bourdon tube 1% filled with water or othersuitable liquid is mounted on and passes through a housing 168. Thelower end of the Bourdon tube is pivotally secured to a link 1 which inturn is pivotally secured to arm 1%. A bracket 112, secured to housing198, adjustably supports an electrical resistance heater element 114. Athermocouple temperature sensing element 116 is secured to the conduit99 at a point therealong. An electrical amplifier 118 connects the coil114 to the thermocouple.

In normal or steady state operation steam passes apertures 96 and 98. Inthe event the conduit temperature rises above a desired level, theincrease is sensed by therm'o'couple 116 and by suitable circuitry inamplifier 118 and resistance coil 114 heats the Bourdon tube. Uponheating, the Bourdon tube end moves leftward as viewed in FIG. 7.Through the link 118 and 1159 also moves leftward, moving plug 164 awayfrom aperture 98 thus allowing greater steam flow and causing alessening of conduit temperature.

In the event the conduit temperature falls below a desired level, thesensing thermocouple and amplifier act to diminish the current toresistance heater 114 and the Bourdon tube end consequently moves to theright, as viewed in FIG. 7, and diminishes the flow opening, plug 104moving into the aperture98. The conduit temperature then risesoccasioned by a lesser flow rate of steam therethrough.

Preferably, the temperature sensing element 116 is placed near an outletheader while the other elements are located near an inlet header, tosubject them to lower stearn temperatures.

Apertures 64 and 96 in the embodirnents insure the passage of a minimumquantity of steam through the conduit at all times.

I claim:

1. A fiuid heater for heating steam and the like including an inletheader and an outlet header, a plurality of conduits extending betweenand communicating with said headers, fluid flow regulating meansdisposed within each of said conduits at a point therealong ear saidinlet header for constantly maintaining the operating temperature ofsaid conduit at an allowable maximum comprising an orifice, means forvarying the size of said orifice including means located externally ofsaid conduit, means sensitive to variances of temperature located on theouter surface of said conduit and near saidoutlet header, saidtemperature sensitive means controlling said fluid flow regulatingmeans, said regulating means adapted to increase fiuid flow within-crease temperature.

2. A fluid heater as claimed in claim 1 wherein each of said pluralityof conduits comprises an element across the conduit passage having twoapertures therein, a second element having an aperture therein, arotatable stem extending through the steam conduit and also through oneaperture of the first element and secured to the second element, atubular coil secured at its bottom end to the other end of the saidstem, an electrical resistance element within said coil, a thermocoupletemperature sensing element secured to the conduit downstream from saidelements and coil, means coupled to the said resistance element and thesaid thermocouple for energizing the resistance element in response totemperatures sensed by the thermocouple, whereby the aperture in thesecond element becomes aligned with the other aperture in the firstelement and the second element moves away from the aperture in the firstelement through which the steam passes, all upon expansion of the coiland whereby increased steam fiow results with increasing temperatures.

-3. A steam conduit adapted to carry steam in a steam heater, element insaid conduit having an aperture therein, a Bourdon tube whose lower endextends into the conduit, a linkage secured to the lower end of theBourdon tube and connected to a plug which is adjacent the saidaperture, heating means for heating the Bourdon tube exteriorly of thesaid conduit, a temperature sensing element disposed on the conduitdownstream from said Bourdon tube, means coupling the heating means tothe said temperature sensing element, whereby the sensing of increasedtemperature results in the heating of the Bourdon tube and movement ofthe lower end of the Bourdon tube to move the plug away from theaperture and thereby increase flow of steam through said conduit.

References Cited in the file of this patent UNITED STATES PATENTS406,704 Collins et a1. July 9, 1889 865,862 Brukenhaus Sept. 10, 19071,164,221 Sarsfield et a1. Dec. 14, 1915 1,881,964 Persons Oct. 11, 19322,437,287 Woods Mar. 9, 1948 2,767,739 Hughes et al Oct. 23, 19562,844,320 Cate July 2 2, 1958 FOREIGN PATENTS 10,518 Great Britain of19(l8 257,593 Great Britain Aug. 14, 1926

1. A FLUID HEATER FOR HEATING STEAM AND THE LIKE INCLUDING AN INLETHEADER AND AN OUTLET HEADER, A PLURALITY OF CONDUITS EXTENDING BETWEENAND COMMUNICATING WITH SAID HEADERS, FLUID FLOW REGULATING MEANSDISPOSED WITHIN EACH OF SAID CONDUITS AT A POINT THEREALONG NEAR SAIDINLET HEADER FOR CONSTANTLY MAINTAINING THE OPERATING TEMPERATURE OFSAID CONDUIT AT AN ALLOWABLE MAXIMUM COMPRISING AN ORIFICE, MEANS FORVARYING THE SIZE OF SAID ORIFICE INCLUDING MEANS LOCATED EXTERNALLY OFSAID CONDUIT, MEANS SENSITIVE TO VARIANCES OF TEMPERATURE LOCATED ON THEOUTER SURFACE OF SAID CONDUIT AND NEAR SAID OUTLET HEADER, SAIDTEMPERATURE SENSITIVE MEANS CONTROLLING SAID FLUID FLOW REGULATINGMEANS, SAID REGULATING MEANS ADAPTED TO INCREASE FLUID FLOW WITHINCREASE IN TEMPERATURE.